Briquetting process and product

ABSTRACT

A method for preparing a fuel pellet/briquette, the method comprising: a) providing cotton gin trash as feed material; b) heating the feed material to a temperature of at least 75° C.; c) compressing the heated feed materials without addition of a binding agent at a pressure to form the fuel pellet/briquette.

TECHNICAL FIELD

The present invention relates generally to the field of cotton gin trash, and more particularly, to a method for processing cotton gin trash into compressed fuel pellets or fuel briquettes.

BACKGROUND ART

Typically, cotton is either hand-picked or machine picked at the farm. This cotton is usually subsequently processed or ginned into lint, mote, seed and gin trash.

Lint is a clean fibre that is sold on the world market. Lint is the fibre that produces cotton cloth used in all sorts of garments and materials. If it's made of cotton it's made with lint.

Mote is a product that is too valuable to be considered as trash and comprises a product that has not been ginned clean enough during the initial ginning process. The mote is baled to be re-ginned usually at seasons end by a gin that is modified to re-gin mote bales. This process ensures that all of the usable, valuable fibre is realised from the entire crop production. Mote fibre is also valuable as a product. Typically, the items made utilizing mote are items like shoe laces, cotton buds, some strings and any low value items that need cotton. Cotton Seed may have a very high percentage of full intact seed or broken/deformed seeds. Cotton seed may be used for cooking oil production or used for protein meal production for cattle feed in feedlots.

Cotton gin trash mainly consists of plant matter. Any stone or mud is separated from the trash and spread on the soil around the gin site. The make-up of trash is purely plant material, being predominantly cotton plant however sometimes other plant samples originating from plants growing in the field with the cotton plant may also be present. The plant material mainly consists of twigs, leaves, sticks etc. which get entangled with raw cotton which is usually fluffy. Trash is the product containing all of the plant matter and waste cotton fibre that comes from the ginning process. It is made up of small pieces of leaf, twigs and small branches, undersize, broken/cracked seeds and cotton fibre.

Cotton gin trash has long been a nuisance to the cotton industry. Cotton production and processing are important to the economy of any country including Australia. With every bale produced, a significant amount of by-product or “gin trash” is also produced. The amount of gin trash produced per bale varies with the method of harvesting. Spindle-harvested (i.e., harvested by mechanical cotton picker) cotton typically results in 75 to 200 lbs of gin trash per bale. Stripper-harvested cotton may result in 300 to 800 lbs of gin trash per bale. The amount of trash produced by strippers is largely dependent upon whether the stripper includes any extractors or other cleaning devices. Every year the cotton industry must dispose of millions of pounds of gin trash.

Common methods of gin trash disposal include direct land application, composting, and donation to cattle farmers for use as a roughage feed ingredient or supplement. However, due to the availability of large quantities of gin trash, several attempts have been made to leverage gin trash as a valuable commodity. Such attempts have included processing gin trash for use as a component in building materials, using gin trash as a mulch for erosion prevention, and using gin trash as a soil supplement.

It will be clearly understood that any prior art referred to herein does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

The present invention is directed to a method for processing cotton gin trash into compressed fuel pellets or fuel briquettes, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

With the foregoing in view, the present invention in one aspect, resides broadly in a method for preparing a fuel pellet/briquette, the method comprising: a) providing cotton gin trash as feed material; b) heating the feed material to a temperature of at least 75° C.; and c) compressing the heated feed material at a pressure to form the fuel pellet/briquette.

In another aspect, the present invention provides a method for preparing a fuel pellet/briquette, the method comprising: a) providing cotton gin trash as feed material; and b) compressing the feed material at a pressure without addition of a binding agent to the feed material to form the fuel pellet/briquette.

In an embodiment, the feed material is heated to a temperature in the range of 90° C. to 120° C. and more preferably in the range of 100° C. to 110° C.

In one embodiment, the cotton gin trash is de-compressed prior to carrying out step a). The de-compressing of the cotton gin trash may be carried out by depositing the supply of the cotton gin trash into a container having a wide-mouth configuration with an opening therethrough; augering said cotton gin trash within the container by auger assemblies therewithin, said augering step including moving said cotton gin trash in a feed direction flow by rotating action imparted thereto by the auger assemblies thereby decompressing the cotton gin trash; and discharging the de-compressed cotton gin trash from the container.

De-compressing of the cotton gin trash may be required as the normal manner of transporting cotton gin trash is in a compressed bale. In an alternative embodiment, the gin trash may not be de-compressed prior to carrying out step a) and may instead be provided by a cotton processing facility located adjacent a feeding assembly positioned for feeding the gin trash material in step (a). Providing a gin trash producing facility adjacent the feeding assembly is highly advantageous because this alleviates the need for transporting compressed bales of gin trash over long distances thereby reducing freight costs.

In an embodiment, the step of providing the feed material in step a) is preceded by regulating the supply of the feed material. The supply of the feed material may be regulated by a regulating auger assembly that regulates the supply of the feed material to step a).

In an embodiment, step b) comprises compressing the heated feed materials in a die. Preferably, the method comprises compressing the feed material into the die with a bore section positioned axially relative to the piston, wherein each stroke of the piston directs the compressed feed material into a bore section of the die.

In an embodiment, the method further comprises the step of cooling the compressed fuel pellets/briquettes.

Preferably, the portion of the immature cotton fiber content of the gin trash removed is at least about seventy-five percent.

In an embodiment, the step of compressing the feed material comprises pressing the feed material by successive strokes of a piston.

In an embodiment, the method further comprises the step of cutting one or more of the compressed pellets/briquettes into smaller units.

Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

Various embodiments of the invention will be described with reference to the following drawings, in which:

Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

FIG. 1 is a first perspective view of system and method for processing gin trash in accordance with a first embodiment.

FIG. 2 is a second perspective view of the system and method for processing cotton gin trash in accordance with a first embodiment.

FIG. 3 is an end view of the system and method for processing cotton gin trash in accordance with the first embodiment.

FIG. 4 is a second end view of the system and method for processing cotton gin trash in accordance with the first embodiment.

FIG. 5 is a schematic view of a compression system for compressing cotton gin trash in accordance with the first embodiment.

FIG. 6 is a flowchart summarising the method of processing the gin trash in accordance with a second embodiment.

DESCRIPTION OF EMBODIMENTS

This invention pertains to pellets, briquettes similar compacted products containing multiple components and having a composition tailored to meet specific requirements for a given application.

Like reference characters denote like parts in the drawings.

FIG. 1 illustrates a system 100 for preparing fuel briquettes from cotton gin trash, according to an exemplary embodiment of the present invention. A quantity of compacted gin trash may be initially provided in the form of compacted gin trash bales 12. The gin trash bales 12 are moved from a storage facility (not shown) such as a storage shed and positioned onto a bale feeder assembly 14. The bale feeder assembly 14 typically comprises a conveyor feeding belt 15 that is mounted on a conveyor belt assembly 16 and driven by a motor. The gin trash bales 12 are fed into an automated unpacking assembly 18 that removes any packaging or netting that wraps the gin trash bales 12. After the removal of the bale packaging, the unpacked bales are released onto a feed-out wagon 22. The feed-out wagon 22 is advantageously positioned in relation to the bale feeder assembly 14 at a relatively lower elevation from the ground, such that the unpackaged bales fall into the feed-out wagon 22 under the effect of gravity. Falling of the unpackaged bale into the feed-out wagon 22 also results in the splitting of the bale into smaller parts. The feed-out wagon 22 comprises a chain floor with slats that move the now split open bale into an auger assembly 24 that is used for de-compression of the split bale. The auger assembly 24 comprises 3 horizontally positioned auger beaters that are operable to rotate at rotational speed of 750-1000 rpm. The auger assembly 24 when activated assists in decompression of the baled trash into a fluffy de-compressed gin trash 25. A skilled person would appreciate that the bale feeder assembly 14, the unpacking assembly 18 and the auger assembly 24 may be automatically controlled by an electronic control mechanism for pre-processing of cotton bales 12 in order to maintaining an optimum production capacity.

The de-compressed gin trash 25 is discharged from the feed-out wagon 22 onto a discharge conveyor belt 26 that is mounted on a discharge conveyor assembly 28. The discharge conveyor belt 26 transports the de-compressed gin trash 25 to an elevated position 27. At the elevated position, the de-compressed trash 25 drops onto a dosing supply conveyor belt 32 mounted on the dosing supply conveyor assembly 34. The dosing supply conveyor assembly may also be readily replaced with a dosing auger assembly in alternative embodiments of the present invention.

The dosing supply conveyor belt 32 is positioned relative to the discharge conveyor belt 26 and positioned in a manner such that at elevated position 27, the de-compressed trash 25 drops onto the dosing supply conveyor belt 32. The de-compressed trash 25 is positioned on a bottom part of the dosing supply conveyor belt 32. The dosing supply conveyor belt 32 comprises chain & slats that drag the de-compressed trash 25 along the bottom of the conveyor belt 32 to allow the de-compressed gin trash 25 to drop into dosing silos 38 positioned underneath the dosing supply conveyor assembly 34. The release of the de-compressed trash 25 into the dosing silos 38 is carried out by the use of a rotary seal 42 positioned adjacent an opening of each of the dosing silos 38. The rotary seal(s) 42 may be actuated using an electronic control mechanism and actuation may be dependent upon the quantity of de-compressed trash 25 contained within the dosing silos 38. For example, the control mechanism may be pre-programmed for actuating the rotary seal(s) 42 when quantity levels of de-compressed trash 25 in the respective associated silo 38 fall below a pre-determined/preset level. Any carry over/surplus de-compressed trash 25 that is not fed into the dosing silos 38 reaches a distal end of the dosing supply conveyor belt and is returned to the feed-out wagon 22 via a return auger assembly 44. The rotary seal 42 works similarly to a rotating door. In an exemplary operation, when the de-compressed trash 25 is required to drop through into the silo 38, the seal 42 spins and the de-compressed trash 25 goes through. When that silo 38 is full, the rotary seal 42 stops spinning and the trash is then dragged to the next rotary seal 42 positioned adjacent the second silo 38. Advantageously a walkway platform 35 is also provided on a frame positioned adjacent the silos 38. The platform 35 allows personnel to monitor and if required control the gin trash transfer operation.

The dosing silos 38 are positioned for feeding the de-compressed gin trash 25 into compression processing assembly modules 50. The dosing silos 38 allow the compression processing assembly modules 50 to be fed a constant and consistent supply of de-compressed trash. The silos 38 in the preferred embodiment have an internal holding volume of 8-10 m3 with a rotating sweep provided on the floor of each silo 38. This sweep allows the product to fall through a feed hole with dimension of approximately 200 mm×500 mm into the feed augers 46 conveying the gin trash released from the silos 38 to the compression processing assembly modules 50.

The feed augers 46 receive the de-compressed trash from the silos 38 and feed it through a feeding assembly into a compression press 52 forming a part of the compression assembly module 50. The compression assembly module 50 assists in densification of the de-compressed gin trash fed into the compression press 52. Densification typically involves two parts; the compaction under pressure of the loose material in the gin trash to reduce its volume and to agglomerate the material so that the product remains in the compressed state after external compression pressure is removed. The resulting solid is termed as a briquette if, roughly, it has a diameter greater than 30 mm. Smaller sizes of the compacted product are normally termed a pellet though the distinction is often arbitrary.

FIG. 5 is an illustration of the compression system housed with the compression assembly module 50. In this module, compaction pressure is applied discontinuously by the action of a piston 52 on the gin trash packed into a cylindrical internal space. The piston may be powered by mechanical coupling and fly wheel or utilise hydraulic action on the piston. Pressure is applied continuously by passing the gin trash through a screw 54 with diminishing volume. These are cylindrical dies with external heating of the die being provided by a heating assembly 55 comprising a heating belt. In a typical operation, the gin trash contained in the die 54 is heated to a temperature in the range of 100° C. to 110° C. It is understood by the applicant that heating the gin trash to such a temperature results in release of plant starches and lignin. These starches and Lignin act as in-situ binding agents thereby alleviating the requirement of using externally added binding agents. The piston 52 gets its reciprocating action by being mounted eccentrically on a crank-shaft with a flywheel. The moving parts are mounted within a very sturdy frame of the module 50 capable of absorbing the very high forces acting during the compression stroke. The most common drive of the flywheel is an electric motor geared down through a belt coupling. A direct-drive system using an internal-combustion or steam engine is also possible and would not change the basic design of the briquetting machine.

The piston 52 may have a top portion that is shaped with a protruding half-spherical section in order to get better adherence of the newly compressed gin trash material to that formed in the previous stroke. The compression module 50 comprises a die 56. The die 56 tapers somewhat towards the middle and then gradually increases in cross section before the end. The exact form of the taper of the die varies between machines and feedstock. The tapering of the die 56 is adjustable and may be adjusted by narrowing a slot in the cylinder. This is achieved by either screw (mechanical) or hydraulic action.

The pressure in the compression section of the compression module 50 is in the order of 110 to 140 MPa. This pressure, together with the frictional heat from the die walls, is in most cases enough to increase operational temperature of the gin trash in the compression chamber at desirable levels (100° C. to 110° C.) resulting in sustained release of plant starches and other plant material that act as in situ binding agents. Controlling the temperature of the material is also very important to prevent excessive burning of the gin trash. Operational temperature maybe optionally reduced by water-cooling the die 56.

If the material is compacted with low to moderate pressure (0.2-5 MPa), then the space between particles is reduced. The reduction of material density is the reason for undertaking briquetting as it determines both the savings in transport and handling costs and any improvement in combustion efficiency over the original material. The ultimate density of a briquette will depend to some extent on a range of factors including, most importantly, the nature of the original material and the machine used and its operating condition as well as other minor factors. The applicant has surprisingly realised that compressing the gin trash in accordance with the method of the present invention not only achieves high densification but also results in improved combustion efficiency because the briquettes as formed by the present invention comprise more combustible material per unit of weight than a known briquette which includes cotton gin trash and a binder as prepared by conventional methods.

The compressed product 57 (briquette or pellet) is extruded out of another end of the die 56 in a continual sausage like form. The compressed product 57 is released into a plurality of cooling passages in the form of cooling pipes 58. The cooling pipes 58 impart a cooling effect to reduce the temperature of the compressed product 57. The compressed product 57 hardens upon cooling as it then travels via the cooling pipes 58. Once the compression product 57 has cooled and hardened enough to maintain its integrity, the sausage shaped product is conveyed to a cutting station (not shown) on a conveyor belt 62 and is cut into 20-30 mm pucks (sliced) before it drops onto another product conveyor belt to be taken to the finished product storage shed where it is loaded by front end loader onto trucks for delivery.

Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art. 

1. A method for preparing a fuel pellet/briquette, the method comprising: a) providing cotton gin trash as feed material; b) heating the feed material to a temperature of at least 75° C.; c) compressing the heated feed materials at a pressure to form the fuel pellet/briquette.
 2. A method in accordance with claim 1 wherein a binding agent is not added to the feed material.
 3. A method for preparing a fuel pellet/briquette, the method comprising: a) providing cotton gin trash as feed material; and b) compressing the feed material at a pressure without addition of a binding agent to the feed material to form the fuel pellet/briquette.
 4. A method in accordance with claim 3 wherein step a) is followed by heating the feed material to a pressing temperature of at least 75° C. before carrying out the compressing step b).
 5. A method in accordance with claim 1 wherein the feed material is heated to a temperature in the range of 90° C. to 120° C. and more preferably in the range of 100° C. to 110° C.
 6. A method in accordance with claim 1 wherein the cotton gin trash is de-compressed prior to step a).
 7. A method in accordance with claim 6 wherein prior to commencing step a) the cotton gin trash is de-compressed by: depositing the supply of the cotton gin trash into a container having a wide-mouth configuration with an opening therethrough; augering said cotton gin trash within the container by auger assemblies therewithin, said augering step including moving said cotton gin trash in a feed direction flow by rotating action imparted thereto by the auger assemblies thereby decompressing the cotton gin trash; and discharging the de-compressed cotton gin trash from the container.
 8. A method in accordance with claim 1 wherein the step of providing the feed material is preceded by regulating the supply of the feed material.
 9. A method in accordance with claim 7, wherein regulating the supply of the feed material comprises feeding the feed material by a regulating auger assembly that regulates the supply of the feed material to step a).
 10. A method in accordance with claim 1 wherein step b) comprises compressing the heated feed materials in a die.
 11. A method further comprising the step of cooling the compressed fuel pellets/briquettes.
 12. A method in accordance with claim 1, wherein the portion of the immature cotton fiber content of the gin trash removed is at least about seventy-five percent.
 13. A method in accordance with claim 1 wherein the step of compressing the feed material comprises pressing the feed material by successive strokes of a piston.
 14. A method in accordance with claim 13 further comprising compressing the feed material into a die with a bore section positioned axially relative to the piston, wherein each stroke of the piston directs the compressed feed material into a bore section of the die.
 15. A method in accordance with claim 1 further comprising the step of cutting one or more of the compressed pellets/briquettes into smaller units. 